A metallocene complex is a compound being used as one of catalyst components in various polymerization reactions, and also is a complex compound which has a central metal bound with one or more cyclopentadienyl or derivatives thereof. Of those, a metallocene complex, which has a central metal bound with one cyclopentadienyl or one derivative thereof, may be referred to as “half metallocene complex” or the like.
A metallocene complex has completely different characteristics (including a catalyst activity for a polymerization reaction) depending on the type of its central metal. For example, the following reports have been made for a metallocene complex which has a central metal of a group III metal or a lanthanoid metal atom.
1. There is disclosed that a complex exemplified by the structural formula (II) can be used as a component of a polymerization catalyst system (see Patent Document 1). The complex disclosed in the document is characterized by including a crosslinking type ligand which has cyclopentadienyl (or a derivative thereof).
In the formula, M represents a group III metal or a lanthanoid metal, A represents a monoanionic crosslinking type ligand having a cyclopentadienyl ring or the like, Q represents a monoanionic ligand, L represents a neutral Lewis base, and w represents an integer of 0 to 3.
2. There is known a hydrido complex represented by (C5Me4SiMe3)LnH2(THF) (Ln represents a group III metal or a lanthanoid metal. Same holds true for the following) (see, for example, Non-patent document 1). A complex represented by (C5Me4SiMe3)Ln(CH2SiMe3)2(THF), which is used as a precursor for the hydrido complex, is also known.
In addition, it is reported that [(C5Me4SiMe3)YH2]4(THF) (tetranuclear complex) of the (C5Me4SiMe3)LnH2(THF) is reacted with styrene to give a 1:1 adduct and shows no polymerization activity (see, for example, Non-patent document 6).
3. It is known that, of the above-mentioned (C5Me4SiMe3)Ln(CH2SiMe3)2(THF), a complex having yttrium (Y) as Ln has no polymerization activity for styrene (see Non-patent document 2).
4. Further, a complex represented by (C5Me4SiMe3)La(CH2(SiMe3)2)2(THF) is known, and it is reported that the complex can serve as a catalyst for a polystyrene polymerization by being combined with methylaminoxane (MAO) or by itself to give an atactic polystyrene (see Non-patent document 3).
However, utility of a metallocene complex (particularly a metallocene complex having a central metal of a group III metal or a lanthanoid metal) as a polymerization catalyst component has not been sufficiently elucidated, so additional studies have been desired.
On the other hand, as a styrene polymer, a syndiotactic styrene polymer (sPS) which can be obtained by a polymerization reaction using a metallocene complex has been industrially produced, as well as an atactic styrene polymer which is referred to as a general grade polystyrene (GPPS), a high-impact resistant polystyrene (HIPS), or the like. Synthesis of sPS was announced by Idemitsu Kosan Co., Ltd. in 1986, and performed by using a catalyst system which includes a titanium metallocene complex (see, for example, Non-patent document 4). As the catalyst system, CpTiX3/MAO or CpTiR3/B(C6F5)3 (Cp represents a substituted or unsubstituted cyclopentdienyl or indenyl, X represents a halide or alkoxy, R represents an alkyl, and MAO represents methylaminoxane) or the like is mainly used.
The thus-synthesized sPS is characterized by having a slightly broad molecular weight distribution irrespective of high syndiotacticity (see, for example, Patent-Documents 2 and 3). Therefore, sPS with a narrower molecular weight distribution has been a compound of interest.
sPS is a polymer which has a high melting point of about 270° C., and advantages such as suitable crystallinity, excellent heat resistance, chemical resistance, and dimension stability, and thus is widely used in industry. Meanwhile, however, it is pointed out that sPS is difficult to be formed or the like.
On the other hand, some reports have been made for synthesis of an ethylene-styrene copolymer (see Non-patent document 5). Each of ethylene-styrene copolymers in those reports is a copolymer having no regio selectivity or a copolymer having no stereoregularity regarding a chain of styrene structural units. Thus, an ethylene-styrene copolymer, which has regio selectivity and high stereoregularity (particularly syndiotacticity) with respect to styrene structural units, has been an interesting compound.
Further, there is reported a method of synthesizing an isoprene-styrene copolymer having styrene structural units with high syndiotacticity using a catalyst of CpTiCl3/MAO (Cp is cyclopentadienyl) (see Non-patent document 10). A catalyst activity in the polymerization reaction is insufficient, so additional improvement has been required. Moreover, many physical properties of the isoprene-styrene copolymer to be synthesized have remained unclarified.
In a polymer of a cyclic olefin, a movement of a polymer main chain of the cyclic olefin is restricted compared to a polymer of a non-cyclic olefin, so the polymer of a cyclic olefins is expected to have excellent heat resistance, strength, and elasticitymodulus. In addition, the cyclic olefin has an expanding potential to be used as an optical material. However, the cyclic olefin compound generally has low polymerization activity because its molecule is bulky, so the number of an effective polymerization catalyst system is limited.
In contrast, there is reported a 1,3-cyclohexadiene polymer which is obtained by polymerizing 1,3-cyclohexadiene, that is one of cyclic olefins, by using a specific nickel catalyst (Non-patent document 7). The polymer is characterized by being a polymer obtained by 1,4-selective addition polymerization of 1,3-cyclohexadiene. Further, it is suggested that the polymer is cis-syndiotactic. However, no specific reports regarding syndiotacticity, molecular weight, and the like thereof have been made.
Further, there are few reports on a 1,3-cyclohexadiene copolymer, so a copolymer of 1,3-cyclohexadiene and another olefin is an interesting compound. As one of a few examples, there is reported a copolymer of 1,3-cyclohexadiene and styrene, which is obtained by anionic copolymerization using alkyllithium. However, the copolymer has no site regularity and stereoregularity.
On the other hand, as a polymer of norbornenes which is one of cyclicolefins, there have been known an open-ring metathesis polymer, a copolymer of norbornenes and ethylene, and the like. Particularly, the copolymer of norbornenes and ethylene has excellent transparency and heat resistance, so the copolymer is expected to be developed as an optical material (see Non-patent document 8). The inventors of the present invention have thought that a copolymer (terpolymer) including norbornenes, ethylene, and an aromatic component has physical properties (for example, UV blocking properties) equal to or superior to those of a copolymer of norbornenes and ethylene, and have made a study of production of the terpolymer.
Further, dicyclopentadiene as one of norbornenes has a C═C double bond derived from a norbornene structure and a C═C bond derived from cyclopentene. A copolymer of dicyclopentadiene and ethylene is also an interesting compound like norbornene. Recently, there has been reported that the copolymer of dicyclopentadiene and ethylene can be synthesized by using a specific Zr complex as a polymerization catalyst (Non-patent document 9). However, a copolymer of dicyclopentadiene and ethylene synthesized according to the reported method, has a limited molecular weight and content of dicyclopentadiene.
Patent Document 1: WO 00/18808
Patent Document 2: JP 62-104818 A
Patent Document 3: JP 62-187708 A
Non-patent document 1: Z. Hou et al., Organometallics, 22, 1171 (2004)
Non-patent document 2: J. Okuda et al., Angew. Chem. Int. Ed., 38, 227 (1999)
Non-patentdocument 3: K. Tanaka, M. Furo, E. Ihara, H. Yasuda, J. Polym. Sci. A: Polym. Chem. 39, 1382 (2001)
Non-patent document 4: N, Ishihara et al., Macromolecules, 19, 2464 (1986)
Non-patent document 5: Mc Knight, A. L.,; Chem Rev. 98, 2587, (1998)
Non-patent document 6: Z. Hou et al., J. Am. Chem. Soc., 126, 1312 (2004)
Non-patent document 7: S. Tanimura et al., Journal of Polymer Science: Part B: Polymer Physics, Vol. 39, 973-978 (2001)
Non-patent document 8: K. Nomura et al., Macromolecules, 36, 3797 (2003)
Non-patent document 9: Adriane G. Simanke et al., Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 40, 471-485 (2002)
Non-patent document 10: Pellecchia, C.; Proto, A.; Zambelli, A., Macromolecules, 25, 4450 (1992)